A rotary damper is conventionally used for the purpose of gently moving a door, or the like, urged in one opening or a closing direction. A rotary damper has a damper housing having a viscous fluid sealed inside and a rotor provided with a rotor blade housed inside the damper housing and a rotor shaft projecting on the rotor blade from the damper housing, and is joined to a gear or other rotating member to damp rotation on the rotor shaft. Such rotary damper may be used as a rotary damper device including a one-way clutch in combination with a one-way clutch for generating a damping force on only rotation in one direction (for example, Patent Document 1).
In the rotary damper device including a one-way clutch according to Patent Document 1, the one-way clutch is configured with a cylindrical inner member having a recessed portion on an outer perimeter portion, a cylindrical outer member having a gear on an inner perimeter portion facing an outer perimeter portion of the inner member, and a gear received in the recessed portion of the inner member to engage with the gear. Also, the gear rotates inside the recessed portion and the outer member rotates independently of the inner member during rotation of the outer member in a positive direction relative to the inner member, and the gear couples to a corner portion formed on one side in a circumferential direction of the recessed portion and the outer member and the inner member rotate as one body during rotation of the outer member in a negative direction relative to the inner member. The configuration is such that the inner member is coaxially coupled to an outer end of the rotor shaft of the rotary damper.